I put about 12000 miles on my 2005----it was totaled in an accident (crazy incident) and I got a 2006 as a replacement. I remember having a couple of issues but really--they were rather minor so it wouldn't stop me if the 2005 you found has been serviced and maintained properly.
The more concerning issue was the servo-brakes----although it's more of a preference issue. The whizzing sound is annoying, but on one particular occasion, when someone pulled out of a gas station and didn't see me---I grabbed hard on the brakes, the servos power assist did their job and saved my ass. I do recall having a brakes indicator come on and brake operation was limited, due to a brake system failure. I forget the specifics but it was related to the servos and covered under warranty. That was early on and no other issues with the brakes after that.
The other issue was the early-version centerstand the 2005's came with----definitely more difficult to lift the GS up on it due to it's position and design. It was redesigned and my 2006 had the updated stand. Much easier to use. The early stand is easy to recognize with it curved crossover bar.
Good luck with the purchase.